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Open Access Research article

The suitability of an uncemented hydroxyapatite coated (HAC) hip hemiarthroplasty stem for intra-capsular femoral neck fractures in osteoporotic elderly patients: the Metaphyseal-Diaphyseal index, a solution to preventing intra-operative periprosthetic fracture

Rishi Chana1*, Reza Mansouri1, Chris Jack1, Max R Edwards2, Ravi Singh3, Carmel Keller4 and Farid Khan1

Author Affiliations

1 Department of Trauma & Orthopaedics, Queen Elizabeth Hospital, South London Healthcare NHS Trust, Stadium Road, Greenwich, London, SE18 4QH, UK

2 Department of Trauma & Orthopaedics, Princess Royal University Hospital, South London, Healthcare NHS Trust, Farnborough Common, Orpington, BR6 8ND, Kent, UK

3 Department of Trauma & Orthopaedics, Darent Valley Hospital, Darenth Wood Road, Dartford, DA2 8DA, Kent, UK

4 Institute of Postgraduate Medicine,Brighton & Sussex Medical School, University of Sussex, Brighton, East Sussex, BN1 9PX, UK

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Journal of Orthopaedic Surgery and Research 2011, 6:59  doi:10.1186/1749-799X-6-59

Published: 18 November 2011

Abstract

This study will seek to identify a measurable radiographic index, the Metaphyseal-Diaphyseal Index (MDI) score to determine whether intra-operative fracture in osteoporotic bone can be predicted.

A 5 year prospective cohort of 560 consecutive patients, undergoing hemiarthroplasty (cemented or uncemented),

    was
evaluated. A nested case-control study to determine risk factors affecting intra-operative fracture was carried out.

The Vancouver Classification was used to classify periprosthetic fracture.

The MDI score was calculated using radiographs from the uncemented group. As a control (gold standard), Yeung et al's

    Canal Bone Ratio
(CBR) score was also calculated. From this, a receiver operating characteristic (ROC) curve was formulated for both scores and area under the curve (AUC) compared. Intra and inter-observer correlations were determined.

Cost analysis was also worked out for adverse outcomes.

Four hundred and seven uncemented and one hundred and fifty-three cemented stems were implanted. The use of uncemented implants was the main risk factor for intra-operative periprosthetic fracture.

Sixty-two periprosthetic fractures occurred in the uncemented group (15.2%), nine occurred in the cemented group (5.9%), P < 0.001. The revision rate for sustaining a periprosthetic fracture (uncemented group) was 17.7%, P < 0.001 and 90 day mortality 19.7%, P < 0.03.

MDI's AUC was 0.985 compared to CBR's 0.948, P < 0.001. The MDI score cut-off to predict fracture was 21, sensitivity 98.3%, specificity 99.8%, positive predictive value 90.5% and negative predictive value 98%. Multivariate regression analysis ruled out any other confounding factors as being significant.

The intra and inter-observer Pearson correlation scores were r = 0.99, P < 0.001.

JRI uncemented hemiarthroplasty has a significantly higher intra-operative fracture rate. We recommend cemented arthroplasty for hip fractures. We propose a radiographic system that may allow surgeons to select patients who are good candidates for uncemented arthroplasty, but it needs prospective validation.

Keywords:
Hip fracture; Uncemented hemiarthroplasty; peri-prosthetic fracture; osteoporosis